Formula SAE Racecar
Driver Aids
Project 05101
Ryan Neward
Henry Berg
Tim Falkiewicz
Nick Lehner
Anthony Magagnoli
Doug Payne
John Schnurr
Table of Contents
1Introduction
2Team Organization
3Needs Assessment
3.1Introduction
3.2Driver Input
3.3Electro-Pneumatic Shift System
3.4Pneumatic Cylinder
3.5Manifold and Solenoid Assembly
3.6Gas Storage Tank
3.7Electric Components
4Concept Development
4.1Possible Solutions
4.1.1Turbocharging
4.1.2Paddle Shifting
4.1.3Clutch Release Control
4.1.4Traction Control
4.1.4.1Brake Actuated Traction Control
4.1.4.2Throttle Controlled Traction Control
4.1.4.3Fuel/Spark Controlled Traction Control
4.1.4.4Dual Rev-Limiter Launch Control
4.1.5Flat Shift
4.1.6Automatic Up-shift
4.2Types of Shift Actuation
4.2.1Mechanical Actuation
4.2.2Electric Solenoid Actuation
4.2.3Hydraulic Actuation
4.2.4Pneumatic Actuation
4.3System Components
4.3.1Cylinder Mounting Location
4.3.2Air System Components
4.3.3Driver Interaction
4.3.4System Monitoring
5Feasibility
6Analysis and Synthesis
6.1Shift Number Calculations
6.2Electrical Calculations
6.2.1Voltage Reduction for RPM Sensor
6.2.2Voltage Reduction for Control Board Power Supply
6.3Valve Sizing
7Specifications
7.1System Specifications
7.2Specifications for the Paddle System
7.3Specifications for the Pneumatic System
8Preliminary Design
8.1Design Elements
8.2Materials
8.3System Operation
8.3.1Paddle/Button Shifting
8.4Flow Charts
8.5Flat Shifting
8.5.1Automatic Up-Shifting
8.5.2Two Stage RPM Limiter
8.5.3Current Gear Display
8.5.4Correct Shift Detection
8.5.5Pneumatic System
8.5.6Microprocessor Code and Pertinent Information
9Future Plans
9.1Focus
9.2Paddle Shifting
9.3Flat Shift
9.4Automatic Up-shift
9.5Launch Procedure
Appendix A - Abbreviations
Appendix B – Microprocessor Code
Appendix C - References
Table of Figures
Figure 1 – FSAE Competition Results
Figure 2 – Steering Wheel Front
Figure 3 – Steering Wheel Back
Figure 5 - Voltage Reduction Circuit
Figure 6 - Control Board Power Supply
Figure 7 - Valve Sizing
Figure 8 - Graph Factor Fg
Figure 9 - Fsg Chart
Figure 10 - Ft Chart
Figure 11 -Complete System Schematic………………………………………………...48
Figure 12 - System Flowchart……………………………………………………………50
Figure 13 – Auto Up-shift Flowchart
Figure 14 - Pneumatic System and Controls……………………………………………..56
Figure 15 - Flat Shift System
Figure 16 - Automatic Up-Shift
Figure 17 - Two Stage Rev Limiter
Figure 18 - LED Gear Display
Figure 19 - Pneumatic System
List of Tables
Table 1 – System Descriptions
Table 2 – Feasibility of Different Systems
Table 3 – Launch Control Feasibility
Table 4 – Launch Procedure Feasibility
1
1Introduction
The Formula SAE is a design competition that challenges SAE student members to design and build an open-wheel formula-style race car. The students must follow a specific set of rules that governs the design and components of the car. However, these rules are more a result of safety concerns than a restriction on advanced design. Therefore it is up to the imagination, creativity and design skills of the students to come up with the best car possible. The design of the car usually takes place over the period of about a year and culminates with the entry into one or all of the three annual international competitions. The three competitions are:
- Formula SAE held in the United States
- Formula Student held in the United Kingdom
- Formula SAE Australasia held in Australia
The three competitions draw teams from all over the globe and may have as many as 140 teams competing against one other.
The idea of this competition is for the students to assume a manufacturing firm has approached them to produce a prototype car for evaluation as a production item. The target sales market for this car is assumed to be the weekend nonprofessional autocross racer. As a result, the car must have very high performance characteristics in the areas of speed, acceleration, braking, handling, safety and reliability. It must also be low in cost, easy to maintain, and tunable for specific driver needs. Due to the fact that the target market for this product is the general public, the car must also be aesthetically pleasing, comfortable and use common parts. The manufacturing firm is looking to produce about four cars per day for a limited production run and the prototype vehicle should not exceed $25,000. The goal of the design team should be to design and fabricate a prototype car that meets all of these criteria. The final product will be compared against all other designs to determine the best overall car.
The car will be judged based on its performance in a variety of both static and dynamic events. These events include: technical inspection, cost, presentation, engineering design, solo performance trails, and high performance track endurance. The first event is the technical inspection. This is worth no points in the competition, but it is required to determine whether the vehicle meets all the FSAE rules and requirements. These rules are laid out in the respective year’s rule book that can be found online.
The cost event is comprised of two different parts. The first part is a written report that the team must present to the Cost Judges prior to the competition. This report must contain a variety of items ranging from a section explaining the bill of materials with receipts and descriptions of the parts to process descriptions that explains any parts that were created from scratch, or purchased and then modified. The second part of this event is a discussion at the competition with the Cost Judges around the team’s vehicle. This evaluates the team’s knowledge and ability to prepare accurate engineering and manufacturing cost estimates. This event is used to teach the students the importance of budget concerns that must be taken into account in any engineering exercise. It also pushes students to learn and understand the techniques used to create any of the components that the team decided to purchase instead of fabricate themselves.
The objective of the presentation event is to determine the team’s ability to prepare and deliver a comprehensive business proposal that will convince the executives of a manufacturing firm to proceed with their design. The team must act as though they are presenting to a room full of executives from all branches of the firm including engineering, finance, marketing, and production, and thus they may not all be engineers. The team must convince this group that the design that they have come up with is the most desired by their target market of weekend nonprofessional autocross racers, and that it can be profitably manufactured. Although the presentation must be about the actual car brought to competition, the quality of the prototype itself has no influence on the score in this event.
The design event is used to evaluate the team’s ability to use their engineering design skills to meet the needs of the market. The team that can best illustrate their use of first-rate engineering practices to meet the design goals and understanding of the design by the team members will score the most points in this event. For this event, it is preferred that the components used within the car are original, student designed parts. These parts are evaluated on the design itself and on the application within the vehicle. Any items that are incorporated into the car as finished components however are not scored on their design, but instead only on the selection and integration of the component into the car to maximize its performance.
The dynamic part of the competition is where the actual performance of the car is tested and the engineering design and application are truly tested. The first event in the dynamic part of the competition is the acceleration run. This event is used to determine the acceleration of the car in a straight line on flat pavement. The car will accelerate from a standing start to a distance of 75 m. It will begin 0.3 m behind the starting line and the time does not begin until the front of the car crosses this line.
The next dynamic event is the skid-pad. The objective of this event is to determine the car’s cornering ability on a flat surface while making a constant-radius turn. The basic layout of the skid-pad consists of a 3.0 m wide path of two circles of 15.25 m diameter in a figure eight pattern. The driver must enter the figure eight and complete one lap on one of the circles to establish the turn, then after completing the first lap, the second lap is timed. The driver must then repeat the same procedure on the second half of the figure eight immediately following the first timed lap. The score is the average of the two times with penalties assessed for knocking over cones or running off course.
The autocross event is the true test of the vehicle’s ability to perform in all areas of overall maneuverability and drivability such as cornering, acceleration, and braking, without the hindrance of competing cars. The autocross course is made up of straights, constant turns, hairpin turns, slaloms, and miscellaneous elements such as chicanes, multiple turns, decreasing radius turns, etc. Average speeds through the course can be expected to be around 45 km/h. The straights may be 60 m in length with hairpin turns at the ends, or shorter 45 m straights with wide turns at the ends. The course is made using cones with the minimum track width being 3.5 m. Penalties are assessed for any knocked over cones, exit from the course, or missed slalom. The score for this event is based on the time it takes for the car to complete the 0.805 km course with penalties assessed.
The final and most important of all the events in the competition is the endurance and fuel economy tests. The endurance portion of this event is worth more overall points in the competition compared to any other event by more than two fold. The endurance event consists of the vehicle running through an autocross type course with an average speed of about 50 km/h and a top speed of approximately 105 km/h. The vehicle must complete the 22 km heat without stopping, except at the midpoint to change drivers. The final score for this event is based on the overall time with the addition of any penalties that may have incurred. The fuel economy score is based on the average liters of fuel per kilometer during the endurance event.
As can be seen by the point breakdown for each of the events throughout the entire competition, the dynamic events are the most important to determine the team’s overall placement. These dynamic events are a measure of the strength of the mesh between the driver and the vehicle. A car that can out-perform anything else on the road is useless of the driver cannot utilize its abilities. Similarly, a driver with exceptional skills cannot maneuver around a track in a vehicle that will not respond to his inputs. It is therefore critical that the interaction between the driver and his machine be as seamless as possible so that the performance of both can be maximized.
As shown below in Figure 1, the FSAE team places lower in the rankings, compared to their other scores, in the events that are very driver dependent. This is what led to the decision to increase driver aids. It was evident that something needed to be done so that the performance of the car could be increased by taking some of the processes out of the driver’s hands and in turn automating them. It could then be possible to design an automated system to give the best possible performance on a more consistent basis.
Figure 1 – FSAE Competition Results
After discussing the need with the FSAE members it was found that one of the most cumbersome operations for the driver to perform was to shift gears. It seems like a simple task, but with unassisted, quick-ratio steering and in a racing situation, taking even one hand off of the steering wheel makes controlling the car even more difficult. By relocating the gear selector for the sequential transmission to the steering wheel itself, the driver would have better control over the car’s steering because he would not have to ever remove his hands from the wheel. By creating electric paddles and buttons on the wheel, the driver can call his next gear and have it pneumatically actuated for him.
In addition to the improved performance by the driver as a result of this design, other systems can be integrated that will allow for the interaction between the driver and the car to be even smoother. A system that will do just that is one in which the engine can automatically be retarded in order to match the speed of the next higher gear without the driver lifting his foot off the gas pedal. In addition, it is possible to take any driver interaction with the shifter out of the equation and just have an automated system that automatically up-shifts through the gears at prescribed optimal rpm levels in an event such as the acceleration run.
Another very difficult task for the driver is “launching” the car, or accelerating the car from a complete stop, in the most efficient manner. The cable-operated clutch is extremely difficult to modulate. The low torque / high horsepower nature of the engine creates a situation where the car either stalls or bogs (launching slowly with the engine well below its optimal power range), or excessively spins its tires. The most effective solution was determined to involve implementing a 2-step rev limiter. The standard rev limiter remains at roughly 12,500 rpm, but the addition of a lower, tunable, limiter that could be used to hold the engine at the ideal rpm in order to get a launch with a proper, limited, amount of wheel spin, effectively getting the car moving faster sooner.
The increased speed and optimization of the shifting process, in combination with the launch control procedure, will combine to decrease the overall time, especially in the acceleration run. The additional control that the driver will possess while shifting will give him better control of the car and increase his ability to be precise with his inputs for the autocross and endurance events.
We will be improving the performance of the car while marginally increasing its cost (< $500). By meeting the goals that we have set forth, the RIT FSAE team will improve their competition results in both the dynamic and static categories.
2Team Organization
Senior Design team 05101 Formula SAE is made up of five mechanical engineers and two electrical engineers. In the early stages of the project, each obstacle was tackled as a team as opposed to splitting up the tasks and assigning smaller groups to solve the problem. However, this method changed as it became clear that there were too many aspects of this project for the team to solve together, due to the finite amount of time that the team could all meet as a group. As a result, each member of the team started to captain his own part of the design, and would report on his progress at the next meeting. The work still remained very blended amongst the group members, but when there was a concern about a certain design aspect, there was always a particular member of the team that one couldlook to for an answer due to their work on that section.
As the team leader, Ryan Neward (ME) was in charge of most of the scheduling and organizational issues. Some of the tasks that he would complete were such things as making sure the entire project was running smoothly, and keeping things organized.
Henry Berg (EE) was the overseer of the project needs. He was in charge of maintaining the direction of our project by keeping the needs in sight and making sure that the team was always designing to meet these needs.
Doug Payne (ME) was the head of the controller portion of the design. He had the most experience with the setup and integration of the controller into the design so that the system would respond the way it was intended.
Anthony Magagnoli (ME) was in charge of the steering wheel design. He has extensive experience in the field of racing, and he is therefore knowledgeable about the necessities of the desired mounting of paddles and buttons by the drivers.
John Schnurr (EE) oversaw the design of the electrical system. He was in charge of making sure that we met our power requirements, and that each of our components could be run off the battery power supply.
Tim Falkiewicz (ME) was in charge of coming up with the necessary equipment for the pneumatic system. This entailed research and assessment of all the different options for air tank sizes, pressures, regulators, and types of gas.
Nick Lehner (ME) oversaw the thermodynamic analysis that was critical to our design. Almost all of our components could not be designed without the knowledge of many different aspects of the system, which all funneled down to trying to answer the issue of the number of shifts we could get from a different combination of inputs.
The chief tasks of each of the group members were just part of the work load that the entire team had to complete. Each member was extensively involved in solving other smaller engineering issues that needed to be answered to effectively complete our design.